Method of bonding diamond with refractory cermet material

ABSTRACT

The diamond and cement materials to be sintered are placed in a hermetic graphite sheathing which is, in turn, arranged inside a sheathing of some low-melting metal. The latter is to be made from a metal whose melting point is lower than the temperature at which diamond will be sintered with the cermet material. The filled-up graphite sheathing is placed into a high-pressure reaction chamber and heated up until the low-melting metal gets soft. Thereafter the temperature and the pressure are raised until they are adequate for diamond to be sintered with cermet material. The softened sheathing of the low-melting material is a hydrostatic medium which provides for a uniform distribution of pressure and temperature over the entire volume of materials being sintered.

lluited States Patent [1 91 Vereschagin et a1.

[ Jan. 15, 1974 METHOD OF BONDING DIAMOND WITH REFRACTORY CERMETMATERIAL Inventors: Leonid Fedorovich Vereschagin,

Kutuzousky prospekt, 10/9, kv. 231; Jury Sergeevich Konyafv, ulitsaFersmana I1, kv. 26, both of Moscow; Alexandr Vasilievich Dovbnya,Podolskyraion, Akademgorodok, ulitsa Tsentralnaya, 10, kv. 112,.Moskovskaya Oblast; Evgeny Valentinovich Polyakov,Belyaevo-Bogorodskoe, 39. kv. 73, Moscow; Novgorodov, AlexandrStepanovich, Timviyazevskaya ulitsa, 34, korpus I, kv. 51, Moscow;Abdulia Ogly Asan-Nuri, Naberezhnaya Shevchenko, /2 kv. 118, Moscow;Polikarp Avtonomovich Paly, ulitsa Zoi i Alexandra Kasmo-demyanskikh, 4,kv. 316, Moscow; Grigory Sergeevich Gevorkov, Oktyabrsky propekt 365,kv. 34, Ljubertsy Moskovsko Oblasti, all of USSR.

Filed: Dec. 21, 1970 Appl. No.: 100,119

U.S. Cl. 51/307, 51/309 Int. Cl B24d 3/06, B24d 3/14 PrimaryExaminer-Donald J. Arnold Attorney-Waters, Roditi, Schwartz & Nissen 57ABSTRACT The diamond and cement materials to be sintered are placed in ahermetic graphite sheathing which is, in turn, arranged inside asheathing of some low-melting metal. The latter is to be made from ametal whose melting point is lower than the temperature at which diamondwill be sintered with the cermet material.

The filled-up graphite sheathing is placed into a highpressure reactionchamber and heated up until the low-melting metal gets soft. Thereafterthe temperature and the pressure are raised until they are adequate fordiamond to be sintered with cermet material. The softened sheathing ofthe low-melting material is a hydrostatic medium which provides for auniform distribution of pressure and temperature over the entire volumeof materials being sintered.

2 Claims, 2 Drawing Figures METHOD OF BONDING DIAMOND WITH REFRACTORYCERMET MATERIAL This invention relates to method used for bondingsuper-hard and cermet materials, in particular to a method of bondingdiamond with refractory cement material, and can be used formanufacturing tools whose cutting tips are made of super-hard material,for instance, boring or abrasive tools.

A conventional method of bonding diamond with super-hard materials,usually powdered ones, consists in sintering them in a high pressurereaction chamber. When sintering is performed, the mass constituted bydiamond grains and cermet material powder is subjected to hot pressingat a pressure of up to 3000 bars. For a firm bonding of particles ofcermet material at sintering temperatures limited by thermal resistanceof diamond, all the mass to be sintered is pressed all around andimpregnated with low-melting metals or their alloys, such as copper,brass, in a high vacuum or an inert medium.

Such impregnation of cermet material makes this method too complicatedand detracts from the mechanical strength of the bond between thediamond and cermet material. Non-uniform distribution of pressure overthe volume of the materials being sintered presents another cause forpoor mechanical strength of the bond between the diamond and cermetmaterial.

Recently a method has found application, whereby diamond is sinteredwith cermet materials in a high vacuum by way of their short-termheating up to a temperature of the order of l400C.

However this method, too, fails to ensure adequately firm bondingbetween the diamond and cermet material due to the sintering processbeing too short and to the formation of considerable thermal stresses.Besides, very high temperatures, such as used in this method, detractfrom the resisting capacity of diamonds, especially synthetic ones,whose thermal resistance is somewhat lower than'that of the naturalones.

The object of this invention is to provide for a method of bondingdiamond with cermet material which would ensure high strength of thebonding without detracting from the thermal resistance of diamond.

It is a specific object of this invention to create the conditions in areaction chamber during sintering, which would ensure a uniformdistribution of temperature and pressure over the entire volume ofmaterials being sintered.

This object is accomplished when carrying out the method of sinteringdiamonds with refractory cermet materials in a high-pressure chamberaccording to this invention, by placing the diamond and cermet materialsare in a hermetic graphite sheathing arranged, in turn, in a sheathingof a low-melting material which softens under pressure at a temperaturelower than that required for sintering said materials and produces ahydrostatic medium; thereby ensuring a uniform distribution of pressureand temperature over the entire volume of materials being sintered.

The produced hydrostatic medium provides for a uniform distribution ofpressure over the entire volume of the materials being sintered, whichensures reliable bonds both between the particles of cermet material andbetween cermets and diamonds. The hydrostatic medium also ensures auniform withdrawal of heat from the entire volume of materials beingsintered, and, a uniform distribution of thermal loads in alldirections. This means that the res'ultant'bonding is free from localthermal stresses or from stresses caused by a nonuniform pressureexerted in one of the directions.

For a better understanding of the invention, the following is adescription of its specific embodiment with reference to the appendeddrawings, wherein:

FIG. 1 shows a high-pressure reaction chamber with a sheathing oflow-melting material inside, said sheathing bein filled with graphitesheathing, every one of which contains a mixture of cermet powder andpolycrystalline diamond;

FIG. 2 is cross section through II-ll of FIG. I.

High-pressure reaction chamber 1 (FIG. 1) accomodates a container 2 madefrom a low-melting material and provided with three cylindrical recessesreceiving graphite sleeves 3 filled up with mixture 4 of diamonds andpowder of refractory cermet material. The sleeves 3 are covered withlids 5 so as to form a hermetic sheathing.

Arranged against the faces of container 2 are washers 6 which are alsomade from a low melting material, and electrical heaters 7 contactingplungers 8.

As the refractory cermet, a powder can be a powder of a hard alloy ofWC-Co or Wc-Ti-Co may be used; while tin, lead, zinc, aluminum or theiralloys may serve as low-melting metals. Materials other than metals arealso suitable, providing their melting points are lower than that atwhich rigid bonds of materials of the mixture being sintered are formed,as a rule lower than l000C.

The process of bonding diamonds with cermets is carried out as follows.

Polycrystals of diamond and cermet powder are mixed up and the resultantmixture is placed in graphite sleeves 3 which have been previously setin the recesses of container 2 made from a low-melting metal.

After the graphite sleeves are filled up with said mixture, they arecovered with lids 5 to produce a hermetic graphite sheathing. Thereaftercontainer 2 is placed in reaction chamber 1, and washers 6 andelectrical heaters 7 are installed. Container 2 in conjunction withwashers 6 produce a hermetic low-melting sheathing. The reaction chamberis pressed between plungers 8 till the pressure exceeds 10000 bars, andelectric current is passed through electrical heaters 7 to heat up thelow-melting metal until it softens.

The softened metal produces a hydrostatic medium ensuring a uniformdistribution of pressure and temperature over the entire volume of thematerials being sin tered. Now the temperature is raised'and thediamonds and the cermet material are sintered together. The sinteringprocess being over, the temperature and pressure are relieved, and thecontainer of low-melting metal is removed from the reaction chamber. Thecontainer and the graphite sheathing are destroyed while the moldedarticles with the diamond sintered to the refractory cermet material aretaken therefrom. These molded articles are used for manufacturing metalmachining or boring tools, for instance, boring bits. For this purposesaid molded articles are machined to impart to them the shape and sizeneeded for their securing in the body of a boring bit by some kind offitting, for instance, by press-fitting.

The above description refers to the preferable embodiment of the methodfor bonding diamond and cermet materials. However the application ofthis method allows also the heating up of a lowmelting container underatmospheric pressure, with subsequent compressing for the high-pressurereaction chamber and raising the temperature to the value adequate forreliable sintering of cermet material with diamond.

The proposed method was used for making mouldings from syntheticpolycrystalline varieties of diamonds (ballases), 5 mm in size, sinteredwith a hard alloy containing 8-15 weight per cent of cobalt. The boringbits provided with cutting tips made from such molded materials provedto be 5-10 times stronger than those with conventionally made cuttingtips.

What is claimed is:

l. A method of bonding diamond and a refractory cermet powder consistingessentially of WC-Co or WC- Ti-Co by sintering under a pressure inexcess of 10 kbars and at a temperature above 1,000C. comprisingcharging said materials in a hermetic graphite shell; placing said shellinside a further shell made of a lowmelting material selected from thegroup consisting of tin, lead, zinc, aluminum and alloys thereof meltingbelow about 1,000C; disposing said shell made of the low-meltingmaterial with said graphite shell contained thereinside in a reactionchamber; heating said shell made of a low-melting material in saidreaction chamber to the melting point of said low-melting material;

elevating the temperature in said reaction chamber so as to effectsintering of the diamond-cermet composition used, sintering saidcomposition being effected in a hydrostatic envelope produced as aresult of heating said low-melting material and said hydrostaticenvelope providing for the throughout the bulk of the materials beingsintered.

2. In a method for bonding diamond and refractory cermet materialconsisting essentially of WC-Co and WC-Ti-Co 'by sintering under highpressures and temperatures in a high pressure reaction chamber, theimprovement comprising subjecting a mixture of the diamond and cermetpowder to sintering temperature range of about l00OC. to about 2000C.and a pressure range of 10 kbars to kbars in a reaction chamber which iscomprised of a graphite shell and a second shell of a low meltingmaterial selected from the group consisting essentially of tin, leadzinc, aluminum, and alloys thereof having a melting point below about1000C, said graphite shell being disposed in said shell of thelow-melting material; whereby on elevating the temperature in saidreaction chamber to effect the sintering, the low melting material meltsbelow the sintering temperature of the mixture and forms a hydrostaticenvelope which provides for a uniform distribution of pressure andtemperature throughout the bulk of the mixture being sintered.

2. In a method for bonding diamond and refractory cermet materialconsisting essentially of WC-Co and WC-Ti-Co by sintering under highpressures and temperatures in a high pressure reaction chamber, theimprovement comprising subjecting a mixture of the diamond and cermetpowder to sintering temperature range of about 1000*C. to about 2000*C.and a pressure range of 10 kbars to 60 kbars in a reaction chamber whichis comprised of a graphite shell and a second shell of a low meltingmaterial selected from the group consisting essentially of tin, leadzinc, aluminum, and alloys thereof having a melting point below about1000*C, said graphite shell being disposed in said shell of thelow-melting material; whereby on elevating the temperature in saidreaction chamber to effect the sintering, the low melting material meltsbelow the sintering temperature of the mixture and forms a hydrostaticenvelope which provides for a uniform distribution of pressure andtemperature throughout the bulk of the mixture being sintered.